this slide is for skin layers and its histological view with labelled diagrams................Best regards my Teachers
Histology of Skin,
integument histology,
integument,
Ali Asadullah
Studento of DVM
3. Tactile epithelioid cells, also known as Merkel cells, are located in
the basal region of the epidermis in both hairless and hairy skin.
Its nucleus is lobulated and irregular, and the cytoplasm is clear .
4. Tactile epithelioid cells are connected to adjacent
keratinocytes by desmosomes.
When associated with an axon, a tactile epithelioid
cell–neurite complex or non-encapsulated tactile
corpuscle is formed.
Specialized areas of skin containing these complexes
are known as tactile hair discs.
Tactile epithelioid cells can also stimulate
keratinocyte growth.
In addition, tactile epithelioid cells can function as
receptors for touch.
5. The dendritic cells located in the epidermis
are called intraepidermal macrophages
(Langerhans cells).
Intraepidermal macrophages are most
commonly found in the upper spinous layer
of the epidermis.
Reported in adult pigs, cats, dogs, human
and rodents.
6. Langerhans cells
Also identified in the stratified
squamous epithelium of the upper
digestive tract, female genital tract and
sheep rumen.
7. Langerhan cell (cont..
At the ultrastructural level, intraepidermal macrophages have a
depressed nucleus and the cytoplasm contains typical organelles.
A unique feature of this cell is distinctive rod- or racket-shaped
granules in the cytoplasm that are known as intraepidermal
macrophage (Birbeck) granules.
Langerhans cells are capable of presenting antigen to lymphocytes
.
8.
9. Dermis
Strong, flexible connective tissue
Cells: fibroblasts, macrophages, mast cells, WBCs
Fiber types: collagen, elastic, reticular
Rich supply of nerves and vessels
Critical role in temperature regulation (the vessels)
Two layers (see next slides)
Papillary – areolar connective tissue; includes dermal
papillae
Reticular – “reticulum” (network) of collagen and reticular
fibers
10. Layers of the dermis
Papillary layer
Reticular layer
13. Epidermis and dermis of (a) thick skin and (b) thin skin
(which one makes the difference?)
14. Hypodermis
“Hypodermis” (Gk) = below the skin
“Subcutaneous” (Latin) = below the skin
Also called “superficial fascia”
“fascia” (Latin) =band;
in anatomy: sheet of connective tissue
Fatty tissue which stores fat and anchors skin (areolar
tissue and adipose cells)
15. Skin appendages
Derived from epidermis but extend into dermis
Include
Hair and hair follicles
Sebaceous (oil) glands
Sweat (sudoriferous) glands
Nails
16. Nails
Of hard keratin
Corresponds to hooves and claws
Grows from nail matrix
17. Hair and hair follicles: complex
Derived from epidermis
Everywhere but palms, soles, nipples, parts of genitalia
*“arrector pili” is smooth muscle
*
Hair papilla
is connective
tissue________________
Hair bulb:
epithelial cells
surrounding
papilla
18. Functions of hair
Warmth – less in man than other mammals
Sense light touch of the skin
Protection - scalp
Parts
Root imbedded in skin
Shaft projecting above skin surface
Make up of hair – hard keratin
Three concentric layers
Medulla (core)
Cortex (surrounds medulla)
Cuticle (single layers, overlapping)
19. Hair color
Amount of melanin for black or brown; distinct
form of melanin for red
White: decreased melanin and increase air bubbles
in the medulla
28. Sweat glands
Entire skin surface
except nipples and
part of external
genitalia
Prevent
overheating
Produced in
response to stress
as well as heat
29. Types of sweat glands
Eccrine or merocrine
Most numerous
True sweat: 99% water, some salts, traces of waste
Open through pores
Apocrine
Axillary, anal and genital areas only
Ducts open into hair follicles
The organic molecules in it decompose with time - odor
Modified apocrine glands
Ceruminous – secrete earwax
Mammary – secrete milk
36. The mammary gland is a
compound- tubuloalveolar
gland.
The secretory units form
lobules separated by
connective-tissue septa.
Mammary Gland
37. Alveoli
Secretory alveoli of the mammary gland
are spherical to ovoid in shape with a
large lumen.
Adjacent alveoli may fuse partially.
The lumen is partially collapsed and
irregular in outline.
Clusters of alveoli form lobules within
the gland.
38.
39. Alveoli
The epithelium of the alveoli varies markedly in height
during various stages of secretory activity.
During active secretion, the basal portion of the
columnar epithelial cells contains a well-developed
rough endoplasmic reticulum.
At the end of the secretory cycle, the epithelial cells are
low cuboidal in shape.
40. Interstitium
The interstitial tissue of the mammary gland provides
important structural support for the secretory units and
contains the blood vessels, lymph vessels, and nerves.
Each secretory unit is surrounded by loose connective
tissue with an extensive plexus of blood and lymph
capillaries.
The interlobular connective tissue is thick and contains the
interlobular ducts and larger blood and lymph vessels.
41. Ducts
The duct system begins with an intralobular duct
which drains into an interlobular duct.
The interlobular duct, in turn, drains into a
lactiferous duct, which is the primary excretory duct
for a lobe.
The intralobular duct epithelium is simple cuboidal.
Spindle-shaped myoepithelial cells may be associated
with these ducts.
42.
43. Teat
The teat, or nipple, contains the terminal part of the duct system.
The lactiferous sinus is continuous with the teat sinus (teat cistern, cavity
of the teat), which is lined by stratified cuboidal epithelium.
The teat sinus empties into one or more papillary ducts (teat canal, streak
canal) leading to the external surface of the teat.
A single papillary duct is present in ruminants while multiple papillary
ducts open separately onto the teat surface of other species.
Horses have 2 papillary ducts, pigs have 2 to 3, cats have
4 to 7, and dogs have 7 to 16.
The papillary duct is lined with stratified squamous epithelium.
44. Teat
The skin of the teat in cows and sows is composed
of a thick, keratinized stratified squamous
epithelium and dermis without hair follicles and
sweat or sebaceous glands.
However, in some domestic species, such as sheep
and goats, the teat may contain fine hairs and sweat
and sebaceous glands.
47. Major Points
The dermis is a dense irregular connective tissue with dermal
papillae that contain capillaries
Many types of nerve endings are found in different parts of
the skin
Epidermal appendages are derived from the epidermis and
include hair follicles, apocrine sweat glands, eccrine sweat
glands, and sebaceous glands
The hypodermis is a fatty connective tissue layer that
surrounds some epidermal appendages